The present invention relates to an optical fiber cable and a method of making it, and more specifically, to a spacer-type optical fiber cable for holding optical fibers in closed spaces provided by a spacer.
One of the problems associated with an optical fiber cable is protecting the optical fibers within the cable from external forces, such as tension, lateral pressure, bending forces and contractile forces caused by temperature changes. These external forces acting against the optical fibers can cause degradation of the transmitting and mechanical characteristics of the fibers.
In an effort to solve the above problems, a "spacer-type" optical fiber cable is known and is considered one of the better structures for this purpose. A spacer-type optical fiber cable usually includes a rod-type spacer provided on its surface with open grooves for loosely holding optical fibers, one or more tension members as a center core of the rod-type spacer, a plurality of optical fibers positionable along the grooves, a tape placed over the rod-type spacer with the fibers therein, and an outer sheath.
As is known, an optical fiber cable is wound around a reel as the last step of its manufacturing process, which reel of cable is then shipped as the finished cable product. Thus, the cable subsequently has to be released from the reel and the cable stretched when using it as a practical communication line. As a result, the optical fibers held in the optical fiber cable receive significant bending stresses.
To deal with such bending stresses, each of the optical fibers is held in the optical fiber cable so as to be positioned in a spiral path along the longitudinal axis of the cable. Thus, the bending stress against each of them can be equalized, and it becomes possible to prevent the fibers from producing differences among each of their transmitting and mechanical characteristics. Therefore, in the prior art, the rod-type spacer of a spacer-type optical fiber cable has on its surface open spiral grooves for holding the optical fibers, so that each of the optical fibers, as mentioned above, is positioned in a spiral along the rod-type spacer's longitudinal axis.
This spacer-type optical fiber cable, however, continues to have problems with it. Namely, continuously arranging the optical fibers in the spiral grooves of the rod-type spacer of the cable in a manufacturing line requires large and complicated mechanisms, especially during the manufacturing step of providing the plurality of optical fibers to the rod-type spacer.